A Russian passenger plane carrying 224 people crashed in a mountainous part of Egypt's Sinai Peninsula on Saturday, with officials saying there are no survivors.

The plane disappeared from radar less than half an hour after taking off early Saturday from the resort city of Sharm El-Sheikh. Almost all the passengers were Russian tourists heading home to St. Petersburg.

Emergency workers who arrived on the scene have recovered 129 bodies so far. They also have recovered a flight recorder from the tail of the plane and sent it to be analyzed.

Authorities are hoping the plane's flight recorders can explain why the plane crashed.

There has been no definitive word on the cause of the crash. Egyptian authorities said the plane was not shot down, while unconfirmed reports said the pilot reported trouble and asked for the nearest landing site just before controllers lost contact with the Airbus jet.

The Metrojet's Airbus A-321 with registration number EI-ETJ that crashed in Egypt's Sinai peninsula, is seen in this picture taken in Antalya, Turkey, Sept. 17, 2015.

IS claim

While no cause has been determined, the Islamic State militant group's Egyptian affiliate claimed responsibility for bringing the plane down, although it offered no evidence.

Russian Transport Minister Maksim Sokov refuted the IS claim, saying it cannot be considered accurate. It is unlikely that IS militants operating in Sinai would have a missile capable of hitting a plane flying that high. The Airbus A-321 had reached cruising altitude of 9,100 meters before it went down.

The Airbus A-321 had 17 children among the 217 tourists on board, along with seven crew members. The passengers were three Ukrainian nationals and 214 Russians.

A couple embraces next to a flight information board at Pulkovo airport in St. Petersburg, Oct. 31, 2015.

Russia's President Vladimir Putin declared a national day of mourning Sunday for victims of the crash.

From Kyrgyzstan, where he began a tour of Central Asia Saturday, U.S. Secretary of State John Kerry offered condolences to the families of those who were on board the plane.

Ambulances line up as emergency workers unload bodies of victims from the crash of a Russian aircraft over the Sinai peninsula at the Kabrit military airport, some 20 miles north of Suez, Egypt, Oct. 31, 2015.

The Metrojet charter flight was operated by the small Russian airline Kogalymavia, also known as Kolavia. It took off from Sharm El-Sheikh at 5:51 a.m., local time (0351 UTC), and disappeared 23 minutes later.

Black boxes

An Egyptian investigative team arrived at the site within hours to examine the debris and locate the flight's recorders, or "black boxes." Russian officials also have opened an investigation into the crash.

Cairo authorities block roads surrounding the morgue expected to receive the bodies of many of the victims, 31 Oct. 2015. (Hamada Elrasam/VOA)

Egyptian authorities say 80 ambulances were sent to the scene and hospitals in six cities and towns were placed on alert, but there were no known survivors. Prime Minister Sharif Ismail was in the city of Ismailiya when he learned of the crash. He interrupted his visit for emergency meetings with government and security officials.

The crash site was about 70 kilometers south of Al-Arish, the largest city in Sinai, on the Mediterranean coast. Egyptian security forces in northern Sinai have been battling a growing Islamic militant insurgency in the area, now led by local affiliates of the Islamic State group, but there have been no incidents involving commercial air traffic.

The area where the plane crashed, known as Hassana or Hasna, was the scene of a World War I battle in 1917 between Britain's Imperial Camel Corps and the Turkish army.